Spawning response latency and egg production capacity of LHRHa-injected mature female sea bass, Lates calcarifer Bloch

Abstract

Mature female sea bass (Lates calcarifer Bloch) were injected once intramuscularly with 20 pg luteinizing hormone-releasing hormone analogue (D-Ala6, Pro'-LHRH-ethylamide) per kg body weight (BW) at different times of the day. Following hormone injection, the incidence of initial spawning and the number of eggs spawned by each fish were recorded. Saline-injected fish did not spawn. Fish spawned at dawn or 33.7-40 h after an LHRHa injection at either 11.00 h or 17.00 h. When LHRHa was administered at 23.00 h or 05.00 h, sea bass spawned during the day or at 38-47.3 h post-injection. Mean egg production levels of 26.8-34.4 x lo4 per kg BWwere higher for fish which spawned at dawn. Low mean egg production levels (6.2-19.9 x lo4 eggs per kg BW) were observed when LHRHa-injected fish spawned during the day. These results demonstrate that the time of initial occurrence of spawning varied with the time of day that LHRHa was administered and that the number of eggs shed was influenced by the time of day that hormone-induced sea bass spawned. Zusammenfassung Verzogerung der Ablaichreaktion und Kapazitat der Eiproduktion von LHRHa-injizierten regenSeebarschweibchen (Lates calcarifer Bloch) Reife Weibchen des Seebarsches Lates calcarifer Bloch wurden einmalig intramuskular mit 20 pg des Juteinizing hormone-releasing hormone" Analogons (D-Ala6, Pro9-LHRH-ethylamid) pro kg Korergewicht zu verschiedenenTa eszeiten injiziert. Nach der Injektion des Hormons wurde die Haufig-Eeit der erzielten Laichreife u n j die Zahl der abgelaichten Eier pro Fisch erfaRt. Salz-injezierte Kontrollfische laichten nicht. Behandelte Fische laichten 34 bis 40 h nach der LHRHa-Behandlung entweder um 11.00 Uhr oder urn 17.00 Uhr. Wenn die LHRHa-Dosis urn 23.00 Uhr oder 05.00 Uhr verabfolgt wurde, laichten die Seebarsche wihrend des Tages oder 38-47 Stunden spater. Die mittlere Zahl der abgelaichten Eier betrug 26,8-34,4 x lo4 pro kg Fisch und war stets hoher fiir Fische die zur D h m erungszeit laichten. Niedrige mittlere Eizahlen (6,2-19,9 x lo4 Eier pro kg Korper ewicht) wurden enielt wenn die behandelten Fische am Tage laichten. Diese Ergebnisse machen ieutlich, dai3 das Erstlaichen mit der Tageszeit der LHRH-Injection variiert und das die Zahl der Eier von der Tageszeit zu der gelaicht wird, beeinflufit ist. RisumC Retardement du frai et capaciti de production d' oeufi des femelles matures de ban-amundi (Lates calcarzfer Bloch) injecteespar un analogue du facreur de liberation de I'honnone luteinisanteDes femelles matures du barramundi (Lates calcarifer Bloch) ont P t i traitees par une injection intramusculaire de 20 pg ar kg de poids de Poisson d'un analogue du facteur de liberation de I' hormone lutiinisante (D-Afa6, Pro9-LHRH-eth lamide) ii differentes heures de la journie. Aprh I'injection, I'incidence initiale du frai et le nombre Joeufs frayis par poissons ont C t i misuris. Les oksons injectis injection de LHRHa ii 11.00 ou 17.00 heures. Quand le LHRAa a it6 administri h 23.00 ou 5.00 heures, les barramundis frayaient pendant la journie ...

Barramundi Aquaculture

“…The spawning rate (number of spawnings of each fi sh over four consecutive days) increases with the dosage used within the dose limits that have been tested (Garcia 1990a ). A dose of 5 micrograms/kg body weight generally produces a single spawning event, while doses of over 10 μ g/kg body weight cause spawnings over 2 -4 nights (Garcia 1990a ).…”

“…In the Philippines (Northern Hemisphere), the spawning season for barramundi is between May and September (Harvey et al . 1985 ), with July and August being the peak period (Garcia 1990a ). In areas close to the equator, spawning may occur throughout the year (Sampath - Kumar et al .…”

“…Hormones are injected either intramuscularly (at the base of the pectoral fi n) or intraperitoneally. LHRHa dosages generally vary from 5 -25 micrograms/kg body weight, but can be as high as 50 -100 micrograms/ kg body weight (Garcia 1990a ;Schipp et al . 2007 ).…”

“…Females with an oocyte diameter of at least 400 microns are suitable for hormonal induction (Garcia 1989b ). Males should have dense sperm (milt) when cannulated, or display expressible milt with gentle abdominal pressure (Garcia 1989b(Garcia , 1990a. The spermatozoa should display a high degree of sperm activation with sea water (Almendras et al .…”

“…Broodstock are generally maintained in either fl oating cages (Garcia 1990a ;SampathKumar et al 1995 ) or tanks (Harvey et al . 1985 ;Almendras et al .…”